The majority of solid cancers are of epithelial origin. A hallmark of epithelial cells are tight and adherens junctions. Tight and adherens junctions seal intercellular spaces and significantly limit the perfusion of anti- tumor agents such as drugs, antibodies, and immune cells within the tumor, thus severely diminishing the efficacy of such therapeutic modalities. The epithelial phenotype of cancer cells also represents a barrier to infection with commonly used adenoviruses (Ads) that target CD46 or the coxsackie-adenovirus receptor (CAR), due to trapping of these receptors in tight and adherens junctions which explains, in part, why these serotypes are inefficient in cancer gene therapy. We found however, that specific human species B adenoviruses, namely Ad3, Ad7, Ad11, and Ad14 (AdB-group 2) that use a yet unknown receptor (receptor X), which is different from CAR and CD46, efficiently infect epithelial cancer cells. This makes these serotypes potential tools for virotherapy of cancer as well as for gene transfer into normal epithelial tissue. In addition, these serotypes are important pathogens, exemplified by recent outbreaks of a highly pathogenic new Ad14 stain (Ad14a) that also uses receptor X. Furthermore, we have shown that recombinant Ad3 dodecahedra (PtDd) formed through interaction of 12 penton bases with protruding fibers can enter epithelial cancer cells and faciliate uptake of Ads (and potentially other tumor agents) for which tight and adherens junctions represent a barrier. Based on the importance of Ad3, 7, 11, and 14 as pathogens and potential vectors for gene therapy, the central goals of this proposal are to identify receptor X, to delineate the mechanism of AdB- group 2 and PtDd uptake in normal and malignant epithelial cells, and to develop AdB-group 2 vectors and PtDd-derivatives as vehicles for gene or drug delivery into epithelial cancers.